Multiple conductor fuse



F. zoDRow ET AL MULTIPLE CONDUCTOR FUSE Filed May 2o, 195o Nov. 29, 1932.

.vdnVO D000 oaovnd. .und 000595600000 INVENTOR F 714777Z Zoafow Z Erw/B197? Schram@ AToRNEY Patented Nov.. 29, 1932 UNITED STATESr PATENT OFFICE FRANZ ZODROW, OF REINIGKENDORF-OST, ANDV ERWIN SCHRANK, OF KALKBERGE,

GERMANY, ASSIGNORS TO WESTINGHOUSE rLELEGLRIC AND MANUFACTURING COM- IPANY, A CORPORATION 0F IPENNSYLVANIA- MULTIPLE CONDUCTOR FUSE Application led May 20, 1930, Serial No. 453,902, and in Germany May 24, 1929.

further object of our invention is to provide a fuse structure, of the above-designated type, with fusible elements of different current-carrying capacities that shall be ruptured in sequence and in such order that the element of greater resistance shall be inserted in shunt relation to the arc.

Our invention will best be understood by referring to the following specification, in conjunction with the accompanying drawing, wherein:

Figure 1 is a view, in sectional elevation, of a fuse structure embodying our invention.

Fig. 2 is a fragmentary View, in sectional elevation, of a fuse structure embodying a modified form of our invention.

Our invention comprises, in general, an insulating casing l having a closure or cap 2 and a ferrule 3, attached to its respective ends to constitute terminal members for connectin the fuse in an electrical circuit.

uses for protecting high-voltage circuits, have been employed heretofore which comprised a plurality of conductors of different resistance respectively located in separate enclosing'tubes and connected in parallel relation to a single conductor exterior to the tubes. A fuse of this type was found to be particularly effective for interrupting a large amount of energy under short-circuit conditions and could be made relatively small and considerably more eective, when enclosed within a single structure.

The successful operation of a fuse of this type in a circuit having a very high shortcircuit current, results because fusion of the main conductor is e'ected with practically no arcing on account of being bridged by the shunt conductor and because the final interruption of the circuit by the shunt conductor is rendered relatively harmless by the inherent resistance of the conductor which operates as a protective resistor.

Upon rupture of the fusible elements connected in a circuit in which a large amount of energy is present, a considerable amount of gas is evolved that is utilized in our fuse structure for aiding the extinguishincnt of the arcs, in a manner that will be explained more fully hereinafter.

A casing 4 is disposed within the casing 1 and is retained in concentric relation thereto by a washer 5 that is attached to its lower end. The washer 5 abuts against the end of the casing 1 and prevents the longitudinal movement of the casing 4, relative to the casing l, when pressures are developed within it. A. fusible element 6 is disposed within the casing 4 and is retained in central relation thereto by a washer 7 that abuts against the end of the casing and is provided with a central opening through which the fuse wire extends. The enclosing cap 2 is screwed upon the threaded end of the casing 1 to retain the end of the fusible element 6 against the washers 7 and 5 and clamp the-washers 5 and 7 against the casings 1 and 4, respectively.

The end of the casing 1 that is provided i with the ferrule 3, has an extension 8 of conducting material associated therewith that is provided with an inwardly sloping surface 9. A. contact member 11 engages the surface 9 .and is retained in fixed relation to the casing 4 because of its frictional engagement with that surface. The contact member 11 is employed as a releasable closing member for the casing l and also as a conducting contact member to which a fusible element 12 is attached by means of a screw 13. The other end of the fusible element 12 properties, while the usible element l2 is made of tungsten, molybdenum or like material that oers relatively high resistance to current iovv.

A second contact member l5, in the form of a cap, as illustrated in the drawing, is associated With the open end or the tube l in releasable current-carrying engagement with the contact member 11. The Contact member l5 is employed as a closure member for the tube a and also as a terminal member for the fuse element 6 that is soldered thereto, as at 16. rlhe releasable connection between contact members l5 and ll permits separation of them up-on the rupture of the fusible elements 6 and l2, respectively, and the escape of the accumulated gas from Within the casing il, before the gases in the casing l have generated a sucient pressure to release the contact member ll.

The operation of our luse device will now be described: Upon the occurrence of a shortcircuit condition in the circuit in which the device is in series relation, the fusible element 6, which is carrying the greater portion of current, because or" its higher conductivity, will rupture first. rlhe arc established within the casing e will generate gases because of the vaporization of the fusible element 6 and the decomposition of the material of the casing et. Thismaterial is preferably fibre, although any other material that liberates unionized gases, When decomposed by an arc, may be substituted.4 The un-ionized gases are beneficial in cooling the arc stream and providing nuclei upon which the ions in the arc stream recombine to form neutral layers. When the volume of the gas withinthe casing a generates a predetermined pressure, the capV l5 over the end thereof is blown 0E, and the gases and theI arc will be blown from Within the casing.

Because of the greater resistance to current flow oiered by the. arc Within the casing a than that oered by the use element l2, the latter will be ruptured and an are will be established Within the casing l exterior to the casing The arc Within the casing l will effect a generation of gas similar to that heretofore referred to relative to the arc established Within the casing a'. lV hen the volume et gas and the pressure thereof reach a predetermined amount, the Contact member ll will be blown from the end or the casing l, and the gases and the arc Within the casing will be ejected :from it. ln passing vout through the arc path, the un-ionized gas will effect a rapid deionization thereof that Will prevent the arc from re-strilring- -F rom the foregoing description it will be apparent that the rictional engagement between the contact member l5 and the contact member l1, and that-between the contact member llY and the extension 8 should be such that the release ofthe member 15 aeeasea Will require less ell'ort than that required to release the contact member ll.

more r 'd deionization of the arc stream .may be had by providing insulating pellets 17 Within the casings l and d that cool and divide the arc and increase the rate of recombination of the ions of the arc path.

lt is apparent that the errule 3 may be positioned away from the end of the casing l, as sh'oWn in Fig. 2, and a contact member i8 may be arranged to extend downwardly into rictional engagement With the errule 3, as illustrated in this gure. ln this construction, When the contact members l5 and 18 are expelled from the ends ot the casings l and d, the ferrule 3 Will be insulated from the escaping gases and the arc by the casing l that extends beyond the errule. Y

lt Will thus be seen that l have provided a unit fuse structure that combines the operation of two independent fuse devices which are connected in parallel relation in a circuit. rlhe casings for the fusible elements of different resistance are closed by conducting members that are independently blown from the ends of the casings as the fusible elements are ruptured, in sequence, in the presence of a short-circuit current. rlhe initial arc has a greater portion of the current shunted therefrom by the fusible element of greater resistance that is in shunt relation thereto and, by blowing the arcs and the contact Vclosure members from the casings, both of the arcs are extinguished. By passing the un-ionized gas, that is evolved by the decomposition ot the material of the casings, through the arc path as the gas and the arc are blown from Within the casing, the arcs are prevented from re-strilring.

While We have described and illustrated only tvvo embodiments of our invention, it is apparent to those skilled in the art that many changes, additions, omissions and substitutions may be made therein Without departing :trom the spirit and Yscope of our invention, as set forth in the accompanying claims.

We claim as our invention:

l. ln a 'nse structure, the combination with a plurality of concentrically associated tubes supported in fixed relation to each other, of independent fusible elements positioned in `the-respective tubes andv connected in `parallel relation, said elements being ruptured successively upon the occurrence of an overload condition, and separable conducting closure members for the respective tubes connected in circuit With their respective fuse elements, the closure member connected to the fusible element which is first ruptured being Vseparable independently of the other closure member.

2. ln a fuse structure, the' combination With two concentrically associated chambers,

of a fusible element calibrated in accordance with the rating of the fuse structure and dis posed Within one of said chambers, a fusible element presenting a higher resistance to current flow than the first said element and disposed in the other said chamber and separable conducting closure members for said chambers connected to their respective fusible elements, the closure member for the chamber containing the first-mentioned fusible element being connected in circuit through the other closure member and separable independently thereof, said other closure member being1 arranged to remain in circuit after removal of the rst closure mem.- ber.

3. A fuse structure includingl two concentrically associated chambers, a fusible element in each chamber, releasable covers for the respective chambers conductively joined to each other and to the fusible elements, and means for retaining one of said covers on its associated chamber as the other of said y covers is released from its chamber.

el. rllhe combination with a main' and an auxiliary fusible element of diderent current-carrying capacities that are enclosed in separate concentrically disposed' chambers, of separate contact members closing the respective chambers and conductively joined to the respective fusible elements thereof, the said contact members being independently releasable from their lassociated chambers when actuated by the pressure developed therein by the rupture of the corresponding fusible element.

5. The combination With a main fusible element and an auxiliary fusible element which offers considerable resistance to current flow, said elements being enclosed in separate concentrically disposed chambers, of separate contact members for closing the respective chambers and conductively joined to the respective fusible elements, the said contact members being independently releasable from their associated chambers in sequence, as the fusible elements are ruptured..

6. In a fuse structure, the combination of two chambers each containing a fusible element, said elements being connected in parallel relation and being fusible successively upon the occurrence of an overload condition, a separable conducting member closing the, chamber containing the element last to be fused and connected to said element, and

a second conducting member closing the chamber containinga the element first to be fused and connected to said element, the second conductingP member being* connected in circuit through the first conducting member and being,r separable independently thereof.

7. ln a fuse structure, the combination of two tubular members arranged in telescopic relation and providing an inner chamber and an annular chamber encompassing 'the inner chamber, fusible elements disposed in said respective chambersfand connected in parallel relation, the element in; the inner chamber being ruptured first and the element in the annular chamber second upon the occurrence of an overload condition, a conducting member for closing; the annular chamber and connected to the fusible element therein, and a second conducting' member for closing the inner chamber and connected to the fusible.

FRANZ ZDROVV. ERWIN SCHRANK. 

